Kevin Mao, a designer in Shanghai, recently had two of his photos placed on Apple billboards to promote the iPhone 6S camera. He told Mashable how he edited the photos.
For this photo, he used TouchRetouch ($1.99, which “lets you remove unwanted content or objects from your photo”), Snapseed (Free, general purpose photo retouching), and VSCO (Free, general purpose photo retouching).
For this one, he used SKRWT (keystone- and lens-correction), Snapseed, and VSCO.